Fluid actuated engines and engine mechanisms

ABSTRACT

A fluid actuator for use in a fluid injector assembly including a piston arranged for reciprocation in a chamber, the piston including a connected plunger operating in an injection chamber. A control valve member is actuated to apply fluid to the chamber on opposite sides of the piston to reciprocate the piston and plunger. A fluid throttling arrangement is provided to decelerate the piston towards the ends of its stroke. The fluid actuator may also be associated with an engine valve assembly. A fluid actuated engine piston assembly is also described.

TECHNICAL FIELD

This invention relates to fluid actuated engines and engine mechanismsand actuators used therein. In one aspect, the present invention relatesto fluid actuators which are applicable to exhaust and inlet valves orfuel injectors of an engine. In a further aspect, the present inventionrelates to fluid actuated reciprocating internal combustion engines.

BACKGROUND ART

Conventional internal combustion engines are provided with a number ofdifferent operating mechanisms for controlling or operating inlet andoutlet valves for the engine cylinders or in the case of fuel injectedengines for controlling the injectors. Usually such mechanisms take theform of cam shafts, rockers, return springs or other mechanicalactuating elements. Such mechanism suffer a number of disadvantages andlimitations including in the case of valved engines, poor valve cooling,poor lubrication, a lack of ability to maintain alignment of the valveswith their seats, poor control over movement of the valve and anexcessive amount of power which is required to overcome the valveseating springs.

Particular disadvantages associated with fuel injectors include lack offlexibility of injection timing, excessive mechanical components in theinjector drive train, an excessive amount of power wastage in operatingthe injectors and their drive train and a lack of ease of assembly andremovability of the injectors and associated drive train from the engineduring maintenance.

In my International Patent application No. PCT/AU90/00387, I describehydraulically operated fuel injectors and valves for internal combustionengines wherein an actuator which incorporates dual pistons includes aninternal axially extending slide valve for controlling operation of theactuator.

It has been found in practice that the function and control of the abovehydraulically actuated fuel injectors and valves has been limited by theexcessive stroke length of the control valve causing in the case of fuelinjectors an inadequate rate of fuel injection or quantity of fuelinjected or in the case of valves inadequate rate of opening or closingof the valve. In addition, there is no readily accessible means foradjusting stroke length for fine adjustment or an efficient means foraddressing the problems of component wear. A further disadvantage isthat there is no method of addressing the abrupt cessation of motion atstroke end.

In hydraulically operated valves, the above disadvantages lead to alimitation in the number of operational cycles per second and thus theoperational speed of the engine.

In my International Patent Application No. PCT/AU90/00387, I alsodescribe an hydraulically operated reciprocating internal combustionengine wherein an hydraulic actuator is coupled to an engine pistonarranged for reciprocation within a cylinder to move with or causereciprocation of the engine piston. The hydraulic actuator includes anumber of chamber sections as well as a discharge or vent chamberadjacent to the engine piston through which hydraulic fluid is vented.It has been found in practise that the length of the combined cylinderunit of such engines is unreasonably long and that the discharge offluid from the vent chamber is inefficient.

SUMMARY OF THE INVENTION

The present invention aims to overcome or ameliorate one or more of theabove disadvantages or at least to provide an alternative to thearrangements referred to above.

One object of the present invention is to provide a fluid actuator whichwhen applied to a fuel injector, shortens the period required forinjection and raises the rate of injection. A further preferred objectis to provide a means for adjustment of stroke length and provide for agradual cessation of movement at the completion of the stroke of theactuator and injector pistons.

A further object of the present invention is to provide a fluid actuatorwhich when applied to engine valves will lead to an increase in the rateof the opening or closing of valves. A further preferred object is toprovide a means for the adjustment of stroke length and provide for agradual cessation of movement at the completion of the valve stroke.

Yet a further object of the invention is to improve the functioning offluid actuated engines of the above described type by shortening theoverall length of the combined cylinder unit by the elimination of thevent chamber adjacent to the engine piston. A further preferred objectis to provide an engine wherein the hydraulic fluid previouslydischarged through the vent chamber is diverted to do useful work.

Other objects and advantages of the invention will become apparent fromthe following description.

The present invention thus provides in a first aspect a fluid actuatorassembly for use with an engine operating mechanism, said fluid actuatorassembly including a chamber, a piston arranged for reciprocatingmovement within said chamber, an actuating member extending from one endof said piston and through said chamber and comprising an actuatingdevice for said engine operating mechanism, and control valve meansarranged externally of said chamber for controlling the supply of fluidto said chamber, said valve means in a first attitude supplying fluid tosaid chamber to cause said piston and actuating member to move in afirst direction, said valve means in a second attitude supplying fluidto said chamber to cause said piston and actuating member to move in asecond direction opposite said first direction.

The chamber may include first and second opposite ends and means may beprovided for decelerating or cushioning movement of the piston as thepiston approaches at least one end of the chamber. The decelerating orcushioning means may comprise means for limiting escape of fluid fromthe at least one end of the chamber. The decelerating or cushioningmeans may include throttling means on an end of the piston adjacent theone end of the chamber adapted to be received in a bore communicatingwith the chamber through which fluid flows, the throttling meanscooperating with the bore to increasingly reduce flow of fluid from thechamber as the piston approaches the one end thereof.

The throttling means suitably may include land means on the piston, theland means having a cross section which decreases away from the piston.Preferably the bore is formed in a movable plug engaged with one end ofthe chamber.

Decelerating or cushioning means may be provided at the opposite ends ofthe chamber for decelerating or cushioning movement of the piston as itapproaches either end of the chamber. The decelerating or cushioningmeans at the actuating member side of the piston may comprises a flaredportion of the actuating member.

The valve means may include a valve chamber and valve means slidablewithin the valve chamber.

The engine operating mechanism may comprises a fuel injector in whichcase the actuating member comprises a plunger arranged for reciprocationwithin an injection chamber. The injection chamber may communicate withthe control valve means and the fluid for operating the actuatorassembly may comprise the working fluid for an engine for injection uponreciprocation of the plunger.

The injection chamber may communicate with the control valve meansthrough one way valve means and may be arranged to receive fluid fromthe control valve means upon the control valve means causing retractingmovement of the piston.

Alternatively, the engine operating mechanism may comprises an engineexhaust or inlet valve and the actuating member is connected to orformed with a valve head of the engine valve. In this configuration,means may be provided for continuously supplying fluid to one end of thepiston, suitably the actuating member end of the piston. The fluid inthe one end of the chamber may be directed to the opposite end of thechamber upon the piston being advanced into the one end of the chamber.This reduces the flow required from a fluid source to operate theactuator assembly.

In yet a further preferred aspect, the present invention provides afluid actuated engine piston-cylinder assembly including a first fluidchamber, piston means arranged for reciprocating movement within saidchamber, means coupling said piston means to an engine piston so as tomovable therewith, said piston means including first and second spacedapart pistons dividing said chamber into a first chamber section betweensaid first piston and one end of said chamber adjacent said enginepiston, a second chamber section between said first and second pistons,and a third chamber section between said second piston and the oppositeend of said chamber, fluid inlet means communicating with said secondchamber section, valve means for controlling the supply of fluid to saidfirst and third chamber sections from said second chamber section tovary the direction of movement of said piston means, a second fluidchamber adjacent said third chamber section and means for selectivelycommunicating fluid from said first chamber section to said second fluidchamber.

The valve means may comprise a slide valve member arranged for movementin a bore extending longitudinally within the piston means. Thecommunicating means may comprise passage means extending longitudinallyof and within the piston means. Alternatively, the communicating meansmay comprises passage means extending longitudinally of and within theslide valve member.

Cam means may be provided for reciprocating the slide valve member, andthe second fluid chamber may surrounding the cam means for lubricationthereof. The valve member may define within the bore a biasing chamber,and means may be provided for communicating fluid to the biasing chamberfrom the second chamber section for biasing the slide valve membertowards the cam means.

The engine piston is arranged for reciprocating movement within acylinder, and the cylinder may include a cooling jacket and fluid may besupplied to the cooling jacket from the second chamber.

The engine piston assembly described may be used in a multiple formatwith the engine cylinders arranged in any orientation, for examplein-line or radially directed from a common cam shaft carrying a cam orrespective cams.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings which illustratea preferred embodiment of the invention and wherein:

FIG. 1 illustrates in sectional view, an hydraulically operated fuelinjector and associated control valve in a first position;

FIG. 2 illustrates the fuel injector in a second position;

FIG. 3 illustrates in sectional view, a hydraulically operated enginevalve mechanism with the valve held closed;

FIG. 4 illustrates in sectional view, the valve mechanism with the valveat the point of opening;

FIG. 5 illustrates in enlarged view, details of one of a number ofpossible multiple valve configurations;

FIG. 6 is a section through a cylinder unit of an engine according tothe present invention;

FIG. 7 is a rotated section through a part of the cylinder unit of FIG.6 showing part of the modified porting;

FIG. 8 is a further rotated section through a part of the cylinder unitdisplaying another part of the modified porting;

FIG. 9 is a section across the cylinder unit showing a typicalarrangement of the ports;

FIGS. 10 to 13 illustrate in similar views to FIGS. 6 to 9 respectively,an alternative embodiment of cylinder unit according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings and firstly to FIG. 1 there is illustrated anhydraulically actuated fuel injector assembly 10 incorporating a fluidactuator assembly 11 according to the invention, the actuator assembly11 including a piston 12 and a piston rod 13 which functions in thisembodiment as a fuel injector plunger. The piston 13 is arranged formovement within a cylindrical chamber 14 and the plunger 13 is arrangedto reciprocate within an injector chamber 15 which is an extension ofthe chamber 14. Both chambers 14 and 15 are formed within the body 16which terminates in a fuel injection nozzle 17 of conventional form.

The end of the cylindrical chamber 14 remote from the injector nozzle 17is closed by a removable plug 18 which is in threaded engagement at 19with a thread in the end of the cylindrical chamber 14. This permits theplug 18 to be rotated and thereby be moved into or out of the chamber 14for the purposes of assembly and servicing and for adjusting the strokelength of the piston 12. This may also be achieved for example by theaddition or removal of shims between a head 20 of the plug 18 and thebody 16 of the injector assembly 10 or alternatively by employing asuitable locking device at the outer end of the plug 18 for temporarilylocking the plug 18 against rotation to prevent accidental adjustment.

The piston 12 is double acting and has opposite working faces 21 and 22.Extending from the working face 21 is a central raised land 23. Acentral cylindrical land 24 also projects from the opposite face 22.

The land 23 tapers in cross section away from the face 21 from acylindrical portion 25 to an end surface 25 located a distance from theportion 25 through either a curved or straight side surface 27. The plug18 includes a counterbore 28 aligned with, and adapted to receive theland 23. The counterbore 28 has an internal diameter substantially thesame as the external diameter of the cylindrical portion 25. Thus as thepiston 12 moves towards its maximum retracted position, the land 23moves into the counterbore 28 and as the effective cross section of theland 23 increases due to the tapering surface 27 to approach that of thecounterbore 28, the movement of the piston 12 is decelerated by the evermore restricted fluid flow allowed between the surface 27 and thecounterbore 28.

The land 24 is of a substantially cylindrical form and the piston rod 13is flared outwardly through either a curved or straight blended surface29 to join the land 24. A counterbore 30 having a diameter slightlygreater than the external diameter of the land 24 is formed between thechamber 14 and chamber 15. Thus as the piston 12 moves during theinjection stroke toward its maximum extended position, the blendedsurface 29 moves into the counterbore 30 and as the effective crosssectional area of the piston rod 13 increases towards the land 24 and tothat of the counterbore 30, the movement of the piston 12 is deceleratedby the increasingly more restricted fluid flow between the blendedsurface 29 and the counterbore 30.

The body 16 also has ports 31, 32 and 33 for the entry and exit ofhydraulic fluid. In this case the hydraulic fluid also serve thefunction as the fuel for injection by the injector assembly 10 into thecombustion chamber of the engine for subsequent ignition. The two drainports 31 and 33 may be internally joined prior to exiting the injectorbody 16. The ports 31, 32 and 33 are connected to a valve chamber 34containing a control valve member 35. A passage 36 may connect the port32 to the end of the chamber 34 to supply fluid under pressure to actagainst an end 37 of the valve member 35 which comprises a piston faceto serve as a biasing means for the valve member 35.

Further ports 38, 39, 40 and 41 communicate with the valve chamber 34and with the chamber 14, the ports 38 and 39 being internallyinterconnected and connected via a passage 42 with a gallery 43 whichcommunicates through ports 44 with a bore 45 in the plug 18communicating with the counterbore 28.

The ports 40 and 41 are also internally interconnected and connected toa common passage 46 which is connected via a port 47 to the counter bore30 and through a one way valve 48 and passage 49 to a port 50communicating with the injector chamber 15. A further fuel injectionpassage 51 is connected between the port 50 and needle valve 52 of theinjector assembly 10. The port 32 is connected to a fluid sourcecomprising in this instance a pump 53 associated with an accumulator 54.

The control valve member 35 may be operated to allow fluid to bedisplaced from the chamber 14 through the counterbore 28, central bore45, ports 44, gallery 43, passage 42 and port 38 and through the controlvalve chamber 34 for discharge from the injector body 16 through theport 31 (FIG. 1).

In this position also, fluid is supplied under pressure to the port 34to pass through the control valve chamber 34 and port 40, passage 46,and port 47 into the counterbore 30 and the chamber 14.

This fluid is also supplied via the passage 49 to unseat the check valve48 and to the injection chamber 15 through the port 50, and through thepassage 51 to the needle valve 52. This charges the injector chamber 15with fuel.

The control valve member 35 may be operated by any suitable means whichmay comprise a solenoid 53 as depicted or otherwise may be any othersuitable mechanical or hydraulic means. The valve member 35 is biased byfluid supplied to the end of the valve member 35 through passage 36.Whilst the biasing means for the valve member 35 of this embodimentcomprises fluid pressure, it may comprise a spring or includes a springwhich may be locate in the valve chamber 34 at the end of the valvemember 35.

With the valve member 35 is actuated to the position of FIG. 2, fluid issupplied to the upper end of the chamber 14 from the port 32 and via thepassage 42 to drive the piston 12 downwardly and integral piston rod 13into the injection chamber 15 displacing fluid from the injector chamber15, seating the check valve 48 and forcing fluid through passage 51unseating the needle valve 52 and injecting fluid into the combustionspace of the engine. Simultaneously, fluid is displaced from the lowerend of the chamber 14 below the piston 12 through the counterbore 30,port 47, passage 46, port 41 passing through the control valve chamber34 to be discharged from the injector body 16 through port 33 for reuse.As the piston 12 approaches the end of the chamber 14, the passagebetween the piston rod or plunger 13 and counterbore 30 reduces in crosssection due to the flared nature of the piston rod or plunger 13adjacent the piston 12. This therefore limits or throttles the rate ofescape of fluid from the lower end of the chamber 14 to thereby cushionthe movement of the piston 12 towards the end of its stroke.

When the valve member 34 is returned to the position of FIG. 1, fluid issupplied to the lower side of the chamber 14 below the piston 12 movingthe piston 12 upwardly and withdrawing the attached piston rod orplunger 13 in the injector chamber 15 allowing the unseating of thecheck valve 48 and the supply of fluid through the port 50 into theinjection chamber 15 and priming the needle valve 52 via the passage 50.Simultaneously the movement of the piston 12 displaces fluid from theupper portion of the chamber 14 through the counterbore 28, central bore45, ports 44, gallery 43, passage 42 and port 38 through the controlvalve chamber 34 to exit from the injector body 16 via the port 31 forreuse. As the piston 12 approaches the upper end of the chamber 14defined by the plug 18, the land 23 enters the counterbore 28 which willtherefore increasingly limit the cross-sectional area of the passagebetween the land 23 and counterbore 28 to limit or throttle the rate ofescape of fluid from the upper side of the chamber 14. This willtherefore cushion the piston 12 in its movement towards the plug 18.

Injection pressure is developed by the amplification of fluid pressurewithin the injection chamber 15 during the injection stroke due to thearea differential between the top working surface of the piston 12 andend face of the piston rod or plunger 13 with the mechanism of theinjector tip 17 following existing practice.

Referring now to FIGS. 3 and 4, there is illustrated an application ofthe fluid actuator assembly of the invention to the control of an enginevalve assembly 60 including a valve head 61 having a valve stem 62 whichincludes or which has mounted to it a piston 63 which is of similarconfiguration to the embodiment of FIGS. 1 and 2 and includes lands 64and 65 on opposite sides. The piston 63 is movable within a cylindricalchamber 66 with the end towards the valve head 61 being fixed whilst theend remote from the valve head 61 is in the form of a plug 67 having afine screw thread 68 operating in a similar screw thread 69 within theouter portion of the cylindrical chamber 66 for moving the plug 67 intoor out of the chamber 66 for the purposes of adjusting the stroke lengthof the valve assembly 60. At the outer end of the plug 67, suitablelocking means 70 may be provided for temporarily locking the plug 67against rotation to prevent accidental movement, the locking means 70 inthis embodiment comprising a strap 71 which may be fixed by a screw 72to the body 73 of the assembly.

The land 65 joins the valve stem 62 through either a curved or straightflared section 74 whilst the land 64 is extended to a surface 75 aworkable distance above the adjacent piston face with a similar blendedcurved or straight section 76 therebetween such that the land 64 is oftapering configuration away from the piston 63. The plug 67 includes acounterbore 77 aligned with the land 64 and a further counterbore 78 isprovided in an insert 79 at the opposite end of the body 73. Thus as thevalve assembly 62 moves towards its maximum stroke position in eitherdirection the blended surfaces 74 or 76 move into the counterbores 77and 78 at either end of the chamber 66, the passage for escape of fluiddecreases in cross section such that the movement of the valve assembly60 is decelerated by the ever more restricted fluid flow through theannular passage between the lands 64 or 65 and the bores 77 or 78.

The cylindrical bore 66 has ports 80 and 81 for the entry and exit ofhydraulic fluid. The port 80 communicates with a gallery 82 which allowsthe flow of hydraulic fluid into or out of the cylindrical chamber 66via a central bore 83 and the counterbore 77 in the plug 67 throughports 84 in the plug 67.

The port 81 communicates with a gallery 85 allowing the flow ofhydraulic fluid into or out of the cylindrical chamber 66 via a port 86in the insert 79 containing the counterbore 78.

For ease of assembly the insert 79 may be made as a removable splitcollar as depicted or otherwise may be a component of the chamber 66 andin this latter case the gallery 85 is omitted.

Hydraulic fluid may be supplied under pressure and vented from thechamber 66 by means of a supply system and control valve assemblysimilar to the type described and shown in FIGS. 1 and 2 and in whichlike components have been given like numerals. In this case however, asupply passage 87 extends from the passage 36 to the port 81. Thisalways provides a fluid supply from the pump 53 (or other supply) to thelower end of the chamber 66.

In the position of FIG. 3, hydraulic fluid is supplied through the port32, passages 36 and passage 87 to the gallery 85 and port 86 to thelower end of the chamber 66 to urge the piston 63 upwardly and theengine exhaust or inlet valve head 61 to a closed position. Where thecontrol valve member 35 is actuated by the solenoid 53 to the positionof FIG. 4, the hydraulic fluid is directed from the port 32 by the valvemember 35 through the port 39, through the passages 42 and port 80 tothe gallery 82 to pass through the ports 84 and central bore 83 to theupper end of the chamber 66 to act against the surface 75 and theadjacent face of the piston 63 driving the valve head 61 open (as shownin dotted outline) and expelling hydraulic fluid from the lower end ofthe chamber 66 through the port 86, gallery 85 and passage 87. Thisfluid passes back through the port 32 to join the flow from the pump 53and/or the accumulator 54 to the upper end of the chamber 66 allowing ahigher rate of movement of the valve head 61 and reducing the fluiddemand upon the pump 53 and/or the accumulator 54.

When the valve member 35 is actuated to move back to the position shownin FIG. 3, it closes the supply of pressurised hydraulic fluid to theupper end of the chamber 66 whilst allowing the venting of fluid fromthe upper end of the chamber 66 through the central bore 83, ports 84,gallery 82, port 80, passages 42 and the control valve chamber 34 whichis directed away through port 31 for reuse. The pressure of thehydraulic fluid entering the lower end of the chamber 66 acting againstthe land 65 and the adjacent face of the piston 63 drives the valve head61 closed and expels hydraulic fluid from the upper end of the chamber66. As the piston 63 approaches each end of the chamber 66 its movementis cushioned through the cooperation between the lands 64 or 65 and thecounterbores 77 or 78 respectively in manner as described above and in asimilar manner as described with reference to FIGS. 1 and 2.

In some cases the screw thread of the plug 67 and chamber 66 may beomitted and stroke adjustment be performed by the addition or removal ofshims with the plug 67 and shims retained by any suitable means.

The biasing means of the control valve may include or consist of aspring and a suitable means of limiting the stroke of the control valvemember may also be included.

For ease of assembly the valve guide 88 about the valve stem 62 may takethe form of a split valve guide.

One controlling mechanism may control the operation of any number ofvalves in multi-valved engine applications. Typical connections betweenvalve assemblies are shown in FIG. 5 where the respective galleries 82and 85 are fluidly interconnected. FIG. 5 also shows in enlarged viewthe arrangements for cushioning or decelerating movement of the piston.Of course the arrangement described above may be used with both inletand exhaust valves.

The control valves for controlling the operation of both the injectoractuator and valve actuator are shown and described to be in the form ofslide valves. They may however comprise any form of valve.

Referring now to FIG. 6, there is illustrated in sectional view apiston/cylinder unit 90 for an engine according to a further embodimentof the present invention which may comprise a spark ignition engine or acompression ignition engine and be operated either as a four cycle ortwo cycle engine and for this purpose may incorporate conventional meansfor the supply of fuel and the removal of exhaust products.

As shown, the piston/cylinder unit 90 includes an engine cylinder 91containing a piston 92 arranged for reciprocation in the cylinder 91.Mounted in line with the cylinder 91 but separated therefrom by apartition 93 which seals off the cylinder 10 is a housing 94 whichdefines a cylindrical operating chamber 95 also sealed off by thepartition 93.

Arranged within the chamber 95 is a piston assembly 96 of the typedescribed in my aforementioned International patent application whichincludes a hollow tubular piston rod or sleeve 97 having mounted thereonor formed integrally therewith a pair of spaced pistons 98 and 99 whichare arranged for reciprocation within the chamber 95. The pistons 98 and99 divide the chamber 95 into a supply section 100 between the pistons98 and 99 and opposite end sections 101 and 102 between the piston 98and wall or partition 93, and piston 99 and a further fixed end wall 103of the housing 94.

The piston rod or sleeve 97 includes a series of ports 104, 105, 106,and 107 which communicate with an internal bore 108 within the rod orsleeve 97. The housing 94 includes a port 109 for connection to a supplyof hydraulic fluid. A further hollow housing or casing 110 is located atthe end of the housing 94 opposite the engine cylinder 90 and defines amounting 111 for the housing 94 which may be connected thereto bybolting.

Located within the bore 108 for reciprocating movement therein is aslide valve member 112 which includes spaced lands 113, 114 and 115separated by annular grooves 116 and 117. The land 115 of the valvemember 112 defines in the end of the bore 108, a chamber 118. A returnspring 119 (shown in dotted outline) may be located within the chamber118 to apply a return biasing force to the valve member 112. Thishowever may also be achieved hydraulically or by other means asdescribed further below.

The opposite end of the slide valve member 112 may be fitted with a camfollower 120 for engagement with a rotatable cam 121 supported on arotatable cam shaft 122 which passes through the casing 110 and which issealed thereto.

As shown more clearly in FIGS. 7 and 9, the piston rod 97 which iscoupled to the piston 92 is provided with a pair of elongated passages123 which extend longitudinally of the piston rod 97 open through ports124 into the bore 108. At their opposite ends, the passages 123 openthrough the end of the piston rod 97 at 125 into the casing 110. Afurther passageway 126 extends from the cam casing 110 to a cylinderjacket 127 surrounding the engine cylinder 91. Fluid may also becommunicated from the cylinder jacket 127 through communicating ports128 with coolant chambers 129 within the cylinder head 130 of theengine.

The piston/cylinder assembly 90 described above functions in a similarmanner to that described in my aforesaid International patentapplication. Thus assuming the piston 92 is at the lower end of itsstroke within the cylinder 91 and that the engine of which thepiston/cylinder assembly 90 is a part is a four cycle engine, the camshaft 122 is rotated to cause the cam 121 to move the slide valve member112 within the bore 108 so that hydraulic fluid is supplied through theport 109 to pass into the casing 110, port 106, groove 116 and port 105into the chamber 102. This will cause the piston assembly 96 to bedriven upwardly because the fluid acts between the piston 99 and endwall 103. At the same time fluid in the chamber 101 is forced throughport 107, groove 117, and into the ports 124 and passages 123 to flowinto the casing 101.

The piston 92 will thus be driven upwardly compressing a fuel chargewhich has been supplied into the cylinder 91 by a conventional fuelsupply arrangement.

Ignition of the charge within the cylinder 91 drives the piston 92 andthe coupled piston rod 97 downwardly from the top position whilst at thesame time the cam 121 has retracted the slide valve 112 thereby closingcommunication between the supply port 109 and chamber 102 but openingcommunication between the chamber 102 and port 104 through groove 116.Thus fluid in the chamber 102 which is under high pressure due to theforce applied by the ignited charge to the piston 92 is forced out upondownward movement of the piston 91 through the port 106, groove 116 andport 104 into a gallery 131 where it is directed through port 132 to douseful work for example for driving an hydraulic motor, and thencereturned to a reservoir to be stored for future use. At the same time,the land 115 blocks the port 124 and communication is opened between theport 106 and chamber 101 through the groove 117 and port 107 so thathydraulic fluid is admitted thereto.

Further upward movement of the slide valve member 112 gain by the cam121 then causes fluid to be admitted to the chamber 102 due tocommunication being re-established between the ports 105 and 106 throughthe groove 106. This causes the piston assembly 112 to be displacedupwardly causing the piston 92 to rise in cylinder 91 thereby causingexhaust gases therein to be discharged through an exhaust valve in thehead 130 in conventional fashion. At the same time, the valve member 112opens communication between the chamber 107 and ports 124 due to theland 115 uncovering the ports 124 so that hydraulic fluid is forced fromchamber 101 into the casing 110 for use as before.

Further movement of the cam 121 then causes movement of the slide valvemember 112 to be reversed so that again fluid is directed from thechamber 100 into the chamber 107 whilst chamber 102 is connected to theport 104. This causes the piston assembly 96 to retract carrying with itthe piston 92 which serves to draw in through the inlet valve in thehead 130 of the cylinder 91 a fresh cylinder charge.

Fluid discharged into the cam casing 110 during the above reciprocationacts as a lubricant within the cam casing 110 and then is expelledthrough the passage 126 into the engine cylinder and head jackets 127and 129 acting as a coolant. The fluid may then be directed to asuitable heat exchanger and returned for further use.

In non-fluid cooled applications the fluid may be discharged directlyfrom the cam casing 110 for further use.

The spring biasing means 119 acting against the slide valve member 112may be eliminated and replaced by a passage 133 (see FIGS. 8 and 9)leading from the supply chamber section 100 through the side valvemember 112 to the chamber 118 previously housing the spring biasingmeans to supply this area with hydraulic fluid under pressure to actagainst the slide valve member 112. This fluid acts against the end ofthe valve member 112 which serves as a piston and biases the slide valvemember 112 against the rotatable cam 112.

The slide valve member end which is adjacent the rotatable cam 112 mayhave as a cam follower 120 a ball or roller cam follower or hydrauliclifter or a combination thereof. The slide valve member 112 itself maybe hollow with suitable end fittings to prevent loss of the fluid nowacting as the biasing means. In the above modifications, the springbiasing means 119 may also be retained to act in conjunction with thehydraulic biasing means.

FIGS. 10 to 13 illustrate an alternative embodiment of cylinder/pistonunit 140 similar to the embodiment of FIGS. 6 to 9 and in which likecomponents have been given like numerals. In this case, the passages 123provided in the piston assembly 96 are eliminated and replaced by aninternal passage 141 extending longitudinally of and within the valvemember 112. Ports 142 communicate one end of the passage 142 through theland 115 with an annular groove 143. Communication between the groove143 and chamber section 101 varies in accordance with the position ofthe land 115 which is capable of blocking or allowing this communicationin a similar manner to which the land 115 of the embodiment of FIGS. 6to 9 blocks or opens the ports 124. The other end of the passage 141communicates through ports 114 opening into the casing 110.

This embodiment functions in the same manner as described with referenceto FIGS. 6 to 9 with discharge fluid passing from the chamber 101 andthrough passage 141 into the casing 110 for use as before.

Engines of this type may be single or multicylindered with theircylinders arranged in any suitable configuration and may be of eithertwo or four cycle or interchangeably both. In a typical arrangement, thecylinders may be arranged to extend from a common cam casing whichreplaces the single casing 110 associated with the separate cylinderunits.

Whilst the above has been given by way of illustrative embodiment of theinvention, all such modifications and variations thereto as would beapparent to persons skilled in the art are deemed to fall within thebroad scope and ambit of the invention as defined in the appendedclaims.

I claim:
 1. A fluid actuated engine piston assembly including a firstfluid chamber, piston means arranged for reciprocating movement withinsaid chamber, means coupling said piston means to an engine piston so asto movable therewith, said piston means including first and secondspaced apart pistons dividing said chamber into a first chamber sectionbetween said first piston and one end of said chamber adjacent saidengine piston, a second chamber section between said first and secondpistons, and a third chamber section between said second piston and theopposite end of said chamber, fluid inlet means communicating with saidsecond chamber section, valve means for controlling the supply of fluidto said first and third chamber sections from said second chambersection to vary the direction of movement of said piston means, a secondfluid chamber adjacent said third chamber section and means forselectively communicating fluid from said first chamber section to saidsecond fluid chamber.
 2. A fluid actuated engine piston assemblyaccording to claim 1 wherein said valve means comprises a slide valvemember arranged for movement in a bore extending longitudinally withinsaid piston means.
 3. A fluid actuated engine piston assembly accordingto claim 1 wherein said communicating means comprise passage meansextending longitudinally of and within said piston means.
 4. A fluidactuated engine piston assembly according to claim 1 wherein saidcommunicating means comprises passage means extending longitudinallywithin said slide valve member.
 5. A fluid actuated engine pistonassembly according to claim 1 and including cam means for reciprocatingsaid slide valve member, said second fluid chamber surrounding said cammeans.
 6. A fluid actuated engine piston assembly according to claim 5wherein said valve member defines within said bore a biasing chamber,and means for communicating fluid to said biasing chamber from saidsecond chamber section for biasing said slide valve member towards saidcam means.
 7. A fluid actuated engine piston assembly according to claim1 wherein said engine piston is arranged for reciprocating movementwithin a cylinder, said cylinder including a cooling jacket and whereinfluid is supplied to said cooling jacket from said second chamber.